Stepwise Raw Synthesis Gas Purification via Selective Absorbent Segmentation
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Solution Overview
Problem
Conventional processes for separating accompanying gases from raw synthesis gas, such as the Rectisol process, face issues with the enrichment of aromatics and mercaptans in the absorbent, leading to premature degradation and environmental concerns due to the release of mercaptans during regeneration.
Innovation Solution
A stepwise separation process using a liquid absorbent countercurrently guided through all process steps, where aromatics and methyl mercaptans are separated in distinct absorption steps before the primary separation of H2S, COS, and CO2, with subsequent regeneration and washing to prevent mercaptan enrichment and odor nuisance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single absorption step is used to separate H2S, COS, and CO2 from raw synthesis gas, then the process is simple and efficient for these components, but aromatics and mercaptans become enriched in the absorbent causing premature degradation and environmental problems
Solution Approach 1:
The absorption process is divided into multiple sequential steps: first absorbing H2S, COS, and CO2 together, then performing a second absorption step to remove aromatics and mercaptans. This segmentation prevents harmful substances from accumulating in the absorbent, extending its service life while maintaining separation efficiency for the primary components.
2Productivity
If the absorbent is regenerated by depressurization or stripping, then CO2 and sulfur-containing gases are removed, but mercaptans are expelled together with CO2 causing odor nuisance to the environment
Solution Approach 1:
The regeneration process is segmented into two distinct steps: first, depressurization or stripping removes CO2 and lighter gases; second, hot regeneration at elevated temperatures selectively removes sulfur-containing compounds including mercaptans. This segmented approach separates the release of different substances, preventing mercaptans from being expelled with CO2 and causing odor nuisance.
Solution Approach 2:
The regeneration process utilizes parameter changes, specifically temperature increase during hot regeneration, to selectively remove different substances at different stages. By changing the temperature parameter, mercaptans are effectively separated and removed in a controlled manner rather than being co-expelled with CO2 during depressurization.
3Manufacturing precision
If a selective absorption process is used to separate sulfur-containing gases and CO2 in separate steps, then the gases are kept separate during absorption, but additional absorption steps are required increasing process complexity
Solution Approach 1:
The absorption process is segmented into functionally distinct steps: the first step absorbs H2S, COS, and CO2 together, while the second step specifically targets aromatics and mercaptans. This segmentation achieves high separation purity for different gas groups while organizing the complexity into a systematic, manageable sequence of operations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This process extends the absorbent's service life, reduces environmental impact by separating mercaptans effectively, and maintains the purity of sulfur-containing gases for further processing, particularly in coal gasification-derived synthesis gas streams.
Implementation Method 1
separation of accompanying gases from a raw synthesis gas stream by a liquid absorbent countercurrently guided through all process steps
Implementation Method 2
In a first regeneration step CO2 is removed from the loaded methanol absorbent by depressurization and/or stripping with a gas
Implementation Method 3
In a first regeneration step CO2 is removed from the loaded methanol absorbent by depressurization and/or stripping with a gas
Implementation Method 4
In a second regeneration step the sulfur-containing gases, COS and H2S, are expelled by heating
Data Source
Figure 1
AI summary
A process for the stepwise separation of accompanying gases from a raw synthesis gas stream by a liquid absorbent countercurrently guided through all process steps and circulated via regeneration plants, wherein either the accompanying gases H2S, COS and CO2 are separated in a common absorption step or, in one of the selective absorption steps chiefly H2S and COS are separated and in the next step in flow direction of the gas chiefly CO2 is separated, and in the last step a separation of accompanying gas residues (fine wash) is effected, wherein before the separation of H2S and COS an absorption step chiefly for the separation of aromatics and subsequently an absorption step chiefly for the separation of methyl mercaptan is carried out.